The invention relates to computer networks and communication systems. In particular, the invention relates to a method and apparatus incorporating a computer program for implementing collaborative conferencing between two or more users.
In a traditional computer application, when a user performs an operation with an input device such as a mouse or keyboard, an event is generated by the operating system and passed to the application program for execution. The standard application would interpret the event and perform operations to change its internal data based upon what the user requested. Similar applications include, for example, performing a deletion step in a word processing program or creating a graphic element in a computer aided design (CAD) program.
When the traditional application is expanded from a single user into a multiple user environment, such as simulating a conference over a network or a modem, each user must be able to manipulate the same data and see all of the modifications made to the data. To do this, each machine must interpret and transmit information about what the user is doing and what the user is seeing. There are three basic approaches to accomplish these results. These approaches correspond to three levels of data manipulation referred to as user input, data modification and visual display. Each approach intercepts and transmits information at the particular level. As a result, each approach has specific drawbacks and benefits.
At the highest level, for example, namely the user input level, each machine intercepts its user input and transmits that input to other machines. For example, if the user clicked the mouse at a screen location (100, 150), the machine would transmit a "mouse click" command with those coordinates to other machines in the conference. The drawback of this approach is that it requires that all machines be set up in exactly the same manner including identical hardware operating systems and applications. If one user has an icon or symbol in a different place on his screen than other users, then a mouse click on that icon on one machine will not be a mouse click on the icon on the other machines. As a result, communication between the people using the system quickly breaks down because they are each seeing different things on their respective screens, thereby making this method of conferencing unusable.
At the lowest level, namely visual display, each machine intercepts visual outputs to the screen and sends it to all other users so that they see the same screen. A program which performs such a function is sometimes referred to as a remote control program. Under such schemes one machine acts as a host and contains all of the data that is manipulated. The other machines pass user inputs to the host machine and receive screen change commands back. A drawback of this method of conferencing is that it requires a large amount of information to be transmitted in the form of all or part of the screen memory and as a result it is relatively slow and inflexible. Also, because all the users in the conference share the same information, all users must possess sufficient hardware and software to display the screen information including complex graphical representations.
Both of the aforementioned methods manipulate data through one entry point. In other words, even though multiple users are working on a document, each user is seen as a single entity to the system. As a result, if one user selects text in a word processor and another user types the key, both operations will be considered as originating from one user, and the data may be accidentally destroyed. Thus, the user input and visual display systems are not truly collaborative wherein multiple users may modify the data concurrently.
In mid-level conferencing, application primitives (units of information necessary to duplicate the user's operation on remote machines) are sent from one machine to the other. While this has been done to some extent at the research level, the drawback is that some centralized control is necessary to implement the exchange of primitives. Another drawback is that high performance (speed) computers and expensive computer systems are necessary to implement such mid-level conferencing in real time. Further, with a centralized architecture, performance limitations are incurred because at least two message transmission delays result between the originating work station and the controller and then back. While the time delay may be reduced by inter-work station communications, a controller work station is required and conflicting commands must be reversed or reexecuted.
In summary then attempts have been made to produce collaborative conferencing programs or architectures but these attempts have significant drawbacks. Some of the approaches rely on host, terminal or master slave relationships among the various users. Some systems only work with the same operating system. Some attempts merely allow one user at a time to access the data. In the case of remote systems, the controller requires interpretation of screen change commands which is slow because of the high data volume. In primitive passing systems the problem is alleviated but at the cost of central processing with high performance equipment.